In general, metered-dose inhalers (MDIs) are devices for dispensing medicaments, e.g. in aerosol form, to the lungs. Broadly speaking dispensers such as MDIs are comprised of two components: a container and a delivery device. The container holds the medication, e.g. dissolved or suspended in a propellant under high pressure to maintain a liquid phase. Additionally the container often comprises an internal metering valve, which is designed to release a precisely measured, reproducible dose of medicament when the valve is actuated. The delivery device typically includes an actuator and a mouthpiece. The actuator, which can be triggered by the user, for example by inhalation or manual operation, typically interacts with the metering valve of the container to induce release of a dose. The mouthpiece serves to direct the medication towards the user.
We have previously described a number of dispensers, see for example U.S. Pat. No. 7,721,731. However, it has been found that manufacturing tolerances mean that the length of a container or substance source can vary from container to container. Furthermore, the length of the spout of the container may vary, too.
This can cause problems in dispenser devices wherein the aerosol can is stationary and another part is moved relative to the can to displace its valve and dispense medicament. Typically the other moving part can only move a certain distance (i.e. a predetermined amount of travel) which means that if, for example a can or its valve is relatively short, the valve may not be fully displaced. As a result, a full dose of medicament may not be dispensed.
There have been different approaches taken to overcoming this problem. See, for example, WO2003/080161 or WO2007/029019.
In the above-mentioned previous approaches, the dispenser body and cap are a constant size and the canister is placed in the body at the same position in all dispensers. The variation in the resulting space between the end of the canister and the cap is taken by deformable materials placed atop the container. However, the above solutions do not always provide satisfactory results, so we have appreciated the need for an improved dispenser cap arrangement.